Figure 3.

Schematic summary of signaling pathways mediated by the orexin/receptor system. The binding of orexins to orexin receptor type 1 (OX1R) or OX2R stimulates G_q or G_i subtypes, which subsequently induce the activation of phospholipase C (PLC), phospholipase A (PLA), phospholipase D (PLD) or Adenylyl cyclases (AC), ultimately resulting in an increase in cytosolic Ca²⁺ and a downstream cascade response. In addition, OA binds OX1R and elevates Ca²⁺ by activating nonselective cation channels (NSCCs).